Waterpump

ABSTRACT

An electrically driven waterpump includes a rotor having impellers for feeding fluid. The rotor is housed in a housing. The rotor includes: a working section located in the fluid and contacting the fluid in a main passage of the fluid stirred by the impellers; and a non-working section located in the fluid and apart from the main passage of the fluid. Water repellency is applied to at least either one of an outer surface of the non-working section or a plane of the housing confronting the outer surface of the non-working section with the fluid interposed, so that shear stress of the fluid is reduced, and pump efficiency is improved.

[0001] The present application claims priority from Japanese Patent Application No. 2003-142386 of Hatano et al., filed on May 20, 2003, the entirety of which is hereby incorporated into the present application by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to an electric waterpump for pumping fluids such as engine coolant for vehicles.

[0004] 2. Description of the Related Art

[0005] In conventional electric waterpumps of this kind such as a magnetic coupling pump for engine coolant for vehicles, a rotor having impellers for feeding coolant is located in a housing, as disclosed in Japanese Laid Open Patent Application No. JP10-311290.

[0006] In this waterpump, a magnet section is located in a part of the rotor apart from impellers, while a stator is located around the rotor toward the housing to generate a rotating magnetic field for driving the magnet section when electrified.

[0007] The rotor is submerged in coolant, and is constituted by two parts: a working section which contacts with the coolant in a main passage of the coolant fed by impellers, and a non-working section which is an area apart from the main passage of the fluid and located in the coolant.

[0008] In conventional waterpumps, however, when in service, it is inevitable that shear stress of coolant occurs between an outer surface of the non-working section including the magnet section and a plane of the housing confronting the outer surface of the non-working section with coolant interposed. In other words, friction between the rotor and coolant is prone to restrain the quantity of coolant supplied and the pressure of the coolant in comparison with electricity supplied to the stator. Especially in rapid rotation area where the rotor rotates at over 3000 rpm, for example, increase of shear stress of the coolant becomes conspicuous, which lowers the pump efficiency compared with supplied electricity.

SUMMARY OF THE INVENTION

[0009] The present invention contemplates to solve the above mentioned problem, and therefore, has an object to provide a waterpump capable of reducing shear stress of fluid in the non-working section, and thus capable of improving pump efficiency.

[0010] The waterpump according to the present invention is driven electrically, and includes a rotor having impellers for feeding fluid. The rotor is housed in a housing. The rotor includes: a working section located in the fluid and contacting the fluid in a main passage of the fluid stirred by the impellers; and a non-working section located in the fluid and apart from the main passage of the fluid. Water repellency is applied to at least either one of an outer surface of the non-working section or a plane of the housing confronting the outer surface of the non-working section with the fluid interposed, so that shear stress of the fluid is reduced.

[0011] In the waterpump of the present invention, since at least either one of the outer surface of the non-working section or the plane of the housing confronting the outer surface has water repellency, fluid in the non-working section of the rotor in service reduces shear stress. Consequently, the rotor is able to rotate smoothly with less friction with the fluid.

[0012] Therefore, the waterpump of the present invention is able to improve pump efficiency by reducing shear stress of the fluid in the vicinity of the non-working section, and consequently consumes less electricity.

[0013] Water repellency in this invention refers to a property that enables reduction of shear stress of fluid in the surfaces of the non-working section and the housing in the vicinity of the non-working section. It is sufficient if the surfaces of the non-working section and the housing in the vicinity thereof are enabled to have an enlarged contact angle with fluid or reduced surface energy with fluid. Water repellency can be applied to the surfaces of the non-working section and the housing in the vicinity thereof, for example, by surface treatment such as coating the surf aces of the non-working section and the housing in the vicinity thereof with water repellant like fluorine plastic used for glass coating material by vapor deposition, welding, or dipping, or by plating for forming smooth surface, which is exemplified by electroless nickel plating. Alternatively, water repellency can be applied also by forming the non-working section and the housing from water repellent material such as fluorine plastic, or by mixing water repellent material into the material for forming the non-working section and the housing.

[0014] Waterpump is exemplified by a magnetic coupling pump including a stator in the housing, in which a rotor is provided in its non-working section with a magnet section, and is rotated by a rotating magnetic field generated by the stator. Moreover, this magnetic coupling pump is exemplified by an outer-rotor type magnetic coupling pump in which the stator is located near the rotation center of the rotor and the magnet section is located around the stator, or an inner-rotor type magnetic coupling pump in which a magnet section is located near the rotation center of the rotor and the stator is located around the magnet section.

[0015] Especially in the outer-rotor type pump, the magnet section to be the non-working section of the rotor has a greater radius than in an inner-rotor type pump, and thus the surface area of the non-working section is increased. Accordingly, with water repellency of the surfaces of the magnet section and the plane of the housing confronting the magnet section surface, a significant effect of improving pump efficiency is obtained in comparison with a case where no water repellency is applied.

BRIEF DESCRIPTION OF DRAWINGS

[0016]FIG. 1 is a vertical section of a first embodiment of the waterpump according to the present invention;

[0017]FIG. 2 is a vertical section of a rotor of the waterpump of FIG. 1;

[0018]FIG. 3 is a vertical section of a housing of the waterpump of FIG. 1;

[0019]FIG. 4 is a graph showing a result of CAE analysis of the first embodiment;

[0020]FIG. 5 is a vertical section of a second embodiment of the waterpump according to the present invention;

[0021]FIG. 6 is a vertical section of a rotor of the waterpump of FIG. 5; and

[0022]FIG. 7 is a vertical section of a housing of the waterpump of FIG. 5.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0023] Preferred embodiments of the present invention are now described below with reference to the accompanying drawings. However, the invention is not limited to the embodiments disclosed herein. All modifications within the appended claims and equivalents relative thereto are intended to be encompassed in the scope of the claims.

[0024] FIGS. 1 to 3 illustrate a first embodiment P1 of the waterpump according to the present invention. The waterpump P1 is a magnetic coupling pump for pumping engine coolant W for vehicles. The pump P1 includes a housing 1 which is made from synthetic resin and has therein a rotor 18 with a plurality of impellers 20 for feeding the coolant W.

[0025] The housing 1 includes a pump chamber 2 in which the impellers 20 of the rotor 18 are located, and a motor chamber 6 located below the pump chamber 2. The pump chamber 2 has a ceiling wall 2 a and has a substantially cylindrical shape as a whole. An inlet pipe 3 for introducing the coolant W is projected upward from the ceiling wall 2 a, and an outlet pipe 4 for exhausting the coolant W is projected outwardly from a circumferential wall 2 b.

[0026] The motor chamber 6 includes a circumferential wall 7 having a substantially cylindrical shape, a bottom wall 8 extending from the lower inner part of the circumferential wall 7 and having an annular shape, and a stator section 9 protruding upward from the center of the bottom wall 8. The stator section 9 includes therein a stator 10 for generating a rotating magnetic field when electrified. A member designated by a reference numeral 11 is a circuit board for rotating the rotor 18, on which power transistors for driving the stator 10, and a Hall element for detecting rotation angle of the stator 10, and so on are located. A member designated by a reference numeral 12 is a terminal for supplying electricity to the circuit board 11.

[0027] Fixed in the center of the stator section 9 is a shaft 13 for supporting the rotor 18 rotatably. An E-ring 14 is located proximate to top of the shaft 13 to prevent the rotor 18 from coming off from the shaft 13. The E-ring 14 is required since the rotor 18 is prone to float up when rotating because of negative pressure in the inlet passage 3. When the pump P1 is in service, the rotor 18 rotates at 3000 to 3800 rpm.

[0028] The rotor 18 includes a main body 19 which has a substantially disc shape and has impellers 20 projected upward, and a magnet section 23 which extends downward from the vicinity of the outer edge of the main body 19 to be located around the stator 10, and has a substantially cylindrical shape. The magnet section 23 is driven and rotates by the rotating magnetic field generated by the stator 10. The main body 19 is provided in its center with a bearing 21 which is made from resin or metal capable of reducing friction such that the rotor 18 rotates around the shaft 13 easily. In the foregoing embodiment, the magnet section 23 is made from a material made by mixing magnetic powder into synthetic resin such as polyamide that forms the rotor 18.

[0029] The rotor 18 is submerged in the coolant W in the housing 1, and can be split up into two parts: a working section 25 and a non-working section 27. The working section 25 is a section that contacts with the coolant W in a main passage F of the coolant W fed by the impellers 20. In the illustrated embodiment, the working section 25 refers to an area above the main body 19 having the impellers 20.

[0030] The non-working section 27 is a section apart from the main passage F of the coolant W propelled by the impellers 20. In the illustrated embodiment, the non-working section 27 includes an area below the main body 19 and the magnet section 23 located below the outlet pipe 4. An outer surface 27 a of the non-working section 27 is constituted by an outer circumference 19 a of the main body 19, a lower surface 19 b of the main body 19, an outer circumference 23 a of the magnet section 23, an inner circumference 23 b of the magnet section 23 and a lower end face 23 c of the magnet section 23.

[0031] In the rotor 18 of the pump P1, the outer surface 27 a of the non-working section 27 is provided with a water repellent layer 29 so as to reduce shear stress of the coolant W and improve water repellency.

[0032] The waterrepellent layer 29 is also formed on a confronting plane 16 of the housing 1 which confronts the outer surface 27 a of the non-working section 27 with the coolant W interposed. The confronting plane 16 of the housing 1 is constituted by an inner circumference 2 c of a lower part of a circumferential wall 2 b of the pump chamber 2, an inner circumference 7 a of the circumferential wall 7, a top surface 8 a of the bottom wall 8, an outer circumference 9 a of the stator section 9 and a ceiling surface 9 b of the stator section 9.

[0033] The water repellent layer 29 in the first embodiment is formed by electroless nickel plating. Of course, however, the water repellent layer 29 may be formed by welding which is done, for example, by spraying and melt-and-resolidifying water repellant such as fluorine plastic, or by coating such as vapor deposition. Alternatively, it will also be appreciated to mix water repellent material such as fluorine plastic into the molding material of the rotor 18 and the housing 1, and to form the rotor 18 and the housing 1 by that material such that the outer surface 27 a and the confronting plane 16 have water repellency.

[0034] In the magnetic coupling pump P1, the outer surface 27 a of the non-working section 27 and the plane 16 of the housing 1 confronting the outer surface 27 a have the water repellent layer 29. Accordingly, fluid W in the non-working section 27 of the rotating rotor 18 reduces shear stress, so that the rotor 18 is able to rotate smoothly with less friction with the coolant W as fluid.

[0035] Therefore, the magnetic coupling pump P1 is able to improve pump efficiency by reducing shear stress of the coolant W in the vicinity of the non-working section 27, and consequently consumes less electricity.

[0036] CAE analysis is conducted to verify the improvement of pump efficiency in the first embodiment. As shown in FIG. 4, fluid resistance is reduced at 20% in the first embodiment. The CAE analysis is conducted by simulating a condition that only the magnet section 23 is submerged in 100° C. coolant which includes 50 volume % LLC (Long Life Coolant) and that the magnet section rotates at 3000 rpm, and by calculating resistance values along the lapse of time.

[0037] In the first embodiment, the pump is exemplified by an outer-rotor type magnetic coupling pump P1 in which the stator 10 is located near the rotation center of the rotor 18 and the substantially cylindrical magnet section 23 is located around the stator 10. However, it will also be appreciated to form a water repellent layer 59 similar to the water repellent layer 29 in an inner-rotor type magnetic coupling pump P2 shown in FIGS. 5 to 7, which is a second embodiment of the present invention.

[0038] The pump P2 also includes a housing 31 which is made from synthetic resin and has therein a rotor 48 with a plurality of impellers 50 for propelling coolant W.

[0039] The housing 31 includes a pump chamber 32 in which the impellers 50 of the rotor 48 are located, and a motor chamber 36 located below the pump chamber 32. The pump chamber 32 has a ceiling wall 32 a, and has a substantially cylindrical shape as a whole. An inlet pipe 33 for introducing the coolant W is projected outwardly from the ceiling wall 32 a, and an outlet pipe 34 for exhausting the coolant W is projected outwardly from a circumferential wall 32 b. The top end 43 a of a shaft 43 rotatably supporting the rotor 48 is fixed to a part of the inlet pipe 33.

[0040] The motor chamber 36 includes a stator section 39 having a substantially cylindrical shape, and a disc-shaped bottom wall 38 extending from an inner lower part of the stator section 39. The stator section 39 includes therein a stator 40 for generating a rotating magnetic field when electrified. Located below the stator 40 are a circuit board 41 for rotating the rotor 48, on which power transistors for driving the stator 40 and a Hall element for detecting rotation angle of the stator 40 are located, and a terminal 42 for supplying electricity to the circuit board 41. The lower end 43 b of the shaft 43 rotatably supporting the rotor 48 is fixed to the bottom wall 38, and an E-ring 44 is located proximate to the top end 43 a of the shaft 43 for holding the rotor 48.

[0041] The rotor 48 includes a main body 49 which has a substantially disc shape and has impellers 50 projected upward, and a magnet section 53 which extends downward from the vicinity of the center of the main body 49 to be located inward of the stator 40, and has a substantially cylindrical shape. The magnet section 53 is driven and rotates by the rotating magnetic field generated by the stator 40. Bearings 51 made from resin or metal capable of reducing friction are located in the center of the main body 49 and in a lower part of the magnet portion 53 for smooth rotation of the rotor 48 around the shaft 43. The magnet section 53 is also made from a material made by mixing magnetic powder into synthetic resin material such as polyamide that forms the rotor 48.

[0042] The rotor 48, too, is submerged in the coolant W in the housing 31, and can be split up into two parts: a working section 55 and a non-working section 57. The working section 55 is a section that contacts with the coolant W in a main passage F of the coolant W fed by the impellers 50. In the illustrated embodiment, the working section 55 refers to an area above the main body 49 having the impellers 50.

[0043] The non-working section 57 is a section apart from the main passage F of the coolant W propelled by the impellers 50. In the illustrated embodiment, the non-working section 57 includes an outer circumference of the main body 49 and the magnet section 53. An outer surface 57 a of the non-working section 57 is constituted by an outer circumference 49 a of the main body 49, a lower surface 49 b of the main body 49, an outer circumference 53 a of the magnet section 53, an inner circumference 53 b of a lower part of magnet section 53 below the bearing 51 and a lower end face 53 c of the magnet section 53.

[0044] In the pump P2, too, the outer surface 57 a of the non-working section 57 is provided with a water repellent layer 59 so as to reduce shear stress of the coolant W and improve water repellency. The water repellent layer 59 is also formed on a confronting plane 46 of the housing 31 which confronts the outer surface 57 a of the non-working section 57 of the rotor 48 with the coolant W interposed. The confronting plane 46 of the housing 31 is constituted by an inner circumference 32 c of a lower end part of a circumferential wall 32 b of the pump chamber 32, a top surface 39 a of the stator section 39, an inner circumference 39 b of the stator section 39 and a top surface 38 a of the bottom wall 38.

[0045] In the pump P2, too, the outer surface 57 a of the non-working section 57 and the plane 46 of the housing 31 confronting the outer surface 57 a have the water repellent layer 59. Accordingly, fluid W in the non-working section 57 of the rotating rotor 48 reduces shear stress, so that the rotor 48 is able to rotate smoothly with less friction with the fluid W. Consequently, pump efficiency is improved, and less electricity is consumed.

[0046] In the outer-rotor type pump P1, the magnet section 23 to be the non-working section 27 of the rotor 18 has a greater radius than in an inner-rotor type pump, and thus the surface area of the non-working section 27 is increased. Accordingly, with water repellency on the surface of the magnet section 23 and the plane 16 of the housing 1 confronting the magnet section surface, a significant effect of improving pump efficiency is obtained in comparison with a case where no water repellency is applied.

[0047] Preferred embodiments show the arrangement to apply water repellency both to the outer surface 27 a or 57 a of the non-working section 27 or 57 of the rotor 18 or 48, and to the confronting plane 16 or 46 of the housing 1 or 31. However, it will also be appreciated to apply water repellency to either one of the outer surface 27 a, 57 a or the confronting plane 16, 46.

[0048] Considering the rotating magnetic field for rotating the rotors 18 and 48, clearance between the rotor 18 or 48 and the stator 10 or 40 is desirably narrow. However, more shear stress is prone to be generated as the clearance becomes narrower. In that case, it will be desirable to apply water repellency to either one of, or both of the confronting planes 23 b and 9 a in the pump P1, or to either one of, or both of the confronting planes 53 a and 39 b in the pump P2.

[0049] Although the preferred embodiments show the waterpumps P1 and P2 for supplying the engine coolant W to vehicles, the present invention is not intended to be limited thereby, but may be applied to waterpumps for supplying fluids such as purified water. 

What is claimed is:
 1. An electrically driven waterpump comprising a rotor having impellers for feeding fluid, the rotor being housed in a housing, the rotor including: a working section located in the fluid and contacting the fluid in a main passage of the fluid stirred by the impellers; and a non-working section located in the fluid and apart from the main passage of the fluid, wherein water repellency is applied to at least either one of an outer surface of the non-working section or a plane of the housing confronting the outer surface of the non-working section with the fluid interposed, whereby shear stress of the fluid is reduced.
 2. The waterpump according to claim 1, wherein: the pump is a magnetic coupling pump including a stator in the housing; and the rotor is provided in the non-working section thereof with a magnet section, whereby the rotor is rotated by a rotating magnetic field generated by the stator.
 3. The waterpump according to claim 2, wherein the pump is an outer-rotor type magnetic coupling pump in which the stator is located near the rotation center of the rotor and the magnet section is located around the stator.
 4. The waterpump according to claim 2, wherein the pump is an inner-rotor type magnetic coupling pump in which the magnet section is located near the rotation center of the rotor and the stator is located around the magnet section. 